Catalytic conversion system



Feb. 18, 1947. .1.5. swEARlNGEN CATALYTIC CONVRSION SYSTEM Filed April 27, 1944 Patented Feb. 18, 1947 o cATALr'rrc CONVERSION SYSTEM John E. Swear-Ingen, Chicago, Ill., asslgnor to Standard Oil Companyg. Chicago, 111.', a corporation of Indiana Application April 27, 1944, serial No. 532,954

i l This invention relates to hydrocarbon conversion and hydrogen halide recovery and it pertains more particularly to an improved method and means Vfor isomerizing -light hydrocarbons such as normal butane, normal'pentane, etc., by means of a liquid aluminum chloride-hydrocarbon complex promoted by hydrogen chloride. v

Anobject of my invention is to provide a simplied commercial isomerization process and apparatus .for isomerizing such hydrocarbons as pentane and butane and to minimize the construction and operating costs thereof. A partic- .ular object is to minimize hydrogen chloride losses and to decrease makeup hydrogen chloride requirements. A further object is to provide improved method and means for supplying makeup catalyst to such a system, for handling catalyst in said system, and for recovering hydrogen chloride from catalyst leaving said system.

In hydrocarbon isomerization systems employing active metal halide catalyst there is a gradual f accumulation of catalyst complex and this accumulation must be continuously' or intermitc claims. (cieco-esas) 4 per mol of aluminum chloride could be recovered from this same complex if the stripping were effected by a vaporized-portion of the lcharging stock or productl stream. This fact has, however, been veried by repeated tests and in accordance with my` invention I obtain almost quantltative hydrogenrchloride recovery from withdrawn complex by simplykstrlppin'g it with charge or product vapors -at a temperature withtently withdrawn from the conversion zone. `-It has -been found that such complex contains appreciable amounts' of hydrogen chloride winch is Y loosely bound in the complex itself. 'I'he hydrolysis of s uch complex with water, steam or'sul- `furic acid is undesirablewbecause of the expenseinvolved. the corrosion problems, and the difcul- 'ties of handling the resulting sludge. v It hasbeen proposed that such spent or discarded complex be scrubbed or-countercurrently contacted with incoming liquid charging stock in order to recover hydrogen chloride but tests lhave shown that by this method only about .1 mol of hydrogn chloride caribe recovered per mol of aluminum chloride in the catalyst complex. about l/'1 the total amount available. An object oi my invention is to provide a method and means whereby substantially all of the available hydrogen chloride may be recovered. A further object is to eiect this recovery in simple and inexpensive apparatus and at minimum operating cost. A further object is to provide an improved and integrated isomerization and hydrogen chlo ride recovery system. Otherobjects will` be 'apparent as the detailed description of my invention proceeds.

Since only about .1 mol of hydrogen chloride per mol of aluminum'chloride can be recovered from spent aluminum chloride-hydrocarbon complex by stripping this complex with hot incoming liquid charging stock, it was most surprising ao tional product stripper. The gaseous products v 1 in.theapproximate range of 200 to 400 F., prefproximate range of 300 to 400 F., i. e. aboutv 350 F. at a space velocityof about 1 to 1.5 volumes of charging stock -(liquid basis)v per hour per volume of spent catalyst, I can substantially reduce the "make-up hydrogen chloride requirements. l

Another feature of Vthe invention is the effecting of this stripping-by vapors already available in the system so that no additional heating means are required and so that "the, only 'additional equipment is a small strippingyessel, a few feet of pipe and a i'ew additional valves. The vapors for eecting the stripping may be taken from the reboiler systemgat the basepof the convenfrom the complex stripper may simply be; returned to the eilluent product'stream at a point subsequent to the pressure reduction valve and prior to the pump which withdraws liquids from the base oi' the settler.

Another feature of the system includes preparation of make-.11p catalyst slurry or paste and the injection thereof into the reactor by the'uid pressure of the charging stockstream. Other features will become apparent from the following detailed description read 4in conjunction with the accompanying .drawing which forms a part of this specification and which is a schematic ilow diagram of my improved visomerization system. In the drawing I have illustrated a commercial system for the isomerization of 1725 barrels per stream day of normal butane or normal pentane by means of a liquid aluminum chloride-hydrocarbon complex and added hydrogen chloride. In this system the charging stock from source I0 is introduced through the line I i, a small amount passes through line I2 for introducing make-up stock passes by line llto pump M which ds-l to find that about 7 mol of'hydrogen chloride u charges it through line ,I5 at a rate regulated by labove the distributor plate 22.

flow-rate control i6. When a pentane charge is employed benzene may be added from source l1, by pump I6 to line I5. The charging stock then passes through preheater i9 which may be provided with about 800 squarefeet of heat exchange surface, and thence be discharged by line 20 to a low point in reactor 2| below distributor plate 22. The amount of steam introduced to preheater I9. may be regulated by controller 23. Recycled and make-up hydrogen chloride is introduced to line 20 through line 24. l

Reactor 2| in this case is a vertical cylindrical vessel about feet in diameter by about 40 feet in height designed to withstand operating pressures of at least 300 and preferably about 500 pounds perspuare inch and provided with a corrosion-resistant lining such asA Hastelloy, suitable ceremic material, or glass cloth coated with a corrosion-resistant cement. Hastelloy ls an ironmolybdenum-nickel alloy which is resistant to all concentrations of hot and cold sulfuric and hydrochloric acids; Hastelloy A for example contains 20% iron, 60% nickel and 20% molydbenum. `When fortication of the complex in the reactor 2| is desired, complex is withdrawn through valve 25, cooler25a and line 25b to mixing vessel 26.

v vented through line 44.

The effluent product stream which'leaves the reactor through line 28 passes through pressure Charging stock remaining in mixer 26 from the previous transfer of paste from the mixer to the reactor,will be displaced through line 21 and Avalve 21a into the reactor product line 28 by the incoming complex. Pressure equilibrium will be set up between complex in mixer 26 and reactor v2| and complex will rise in line 21 to the same complex in mixing drum 26 is vented to the blow- Vdown stack through lines 21, 32, and valved line 33. -The complex in mixer 26 will then be at atmospheric pressure and head 34 of mixing vessel 26 .can be removed and solid aluminum chloride added. Conventionally 0.1 to 10, preferably 1 to 3, for instance 2 pounds of aluminum chloride are added per pound of complex contained in the mixing vessel. The head is replaced and mixer 35 is operated to produce a homogeneous paste in mixing vessel 26. Pump 36 is then started andfresh feed is pumped into vessel 26 through lines I2, 32 and 21 displacing the paste of aluminum chloride and complex through line 25h, cooler 25a (which will act as a heater for this service), valve 25, and into reactor 2|. The succession of operations described above will be car` ried out intermittently and with such frequency as to maintain `the desired catalyst activity' in reactor 2|.

reactor by line 31 or from a point above distributor plate by line 36 and introduced bylines 39, 40 and 4I into catalyst storage tanklConversely catalyst may be withdrawn from the storage tank through line 4| andreturned by pump 42 through lines 39 and'g31-*to the base of the reactor Qr through lines 39 and 36 to a point To provide for blanketing of catalyst complex in the storage tank Complex may be drained from the base of the Y reducing valve 45 and thence through line 46 to after-cooler 41 which may require about 1100 square feet of heat exchange surface. The cooled products then pass through line 48 to cold settler 49 which Vmay be a cylindrical vessel about 4 feet by 16 feet provided with overow Weir 50. -Settled catalyst material maybe returned from the base of the cold settler through valved line 5| to catalyst storage tank 3|. Gases may be vented from the top of the settler through line 52 in amounts controlled by back pressure valve 53. In

some cases it may be desirable to scrub hydrogen chloride out of gases thus removed from the top of the cold settler .and in such cases we mayV countercurrently contact or scrub the eilluent gases with a 'cool absorber oil such, for example,

as a portion of the incoming charging stock or a portion of the cooled and caustic washed productV stream. The scrubbing or absorber oil thus employed may either be combined with reactor charge or simply introduced into cold settler 49 depending on its composition.

The remaining liquid product stream consisting essentially of hydrocarbons and dissolved hydrogen chloride is Withdrawn through line 54 and introduced by pump '55 and line 56 at an upper point in product stripper 51. Valve 56 may control the rate of flow in line 56in accordance with the liquid level in cold settler 46.

The product stripper 51 may be a cylindrical 5 vessel about 4 feet in diameter by about 55 feet high and it may be provided with about 20 trays. It should be designed to withstand an operating pressure higher than maximum desirable reactor pressure since the gases which leave thetop thereof through line 59 are recycled directly through line 24 to reactor 2| Without compression. Makeup hydrogen chloride is introduced from source 60 through line 6|.

The stripper isprovided at its base with trapout pan 62 from which liquids are withdrawn through line 63 to reboiler 64. Vapors are returned from this reboiler to the base of the stripper through line 65. Liquids are withdrawn from the base of stripper 51 through line 66 in amounts controlled by vvalve 61 in accordance with the liquid level in the base of stripper 51. The Withdrawn liquid then passes through product cooler 66, thence through line 69`to caustic'wash tank 10 into which caustic is introduced by pump 1| through line 12. Spent caustic is Withdrawn through line `13 and the neutralized product stream is finally withdrawn through lin 14 for water washing and/or fractionation.

The catalyst employed in this system is preferably an 'aluminum chloride-hydrocarbon complex which may be initially prepared (particularly in the case of pentane) by reaction of aluminum chloride with a portion of thecharging stock in the presence of hydrogenchloride. For starting up the process, however, the complex may be prepared from other light saturated such complex should have a nat of hydroIysis of about 300 to 400 calories per gram oi complexand its hydrocarbon content should be at least about 15% but not more than about 40%,

(based on charging stock) is introduced into the reactor with the `charging stock the catalyst complex withdrawn from the reactor contains appreciable -amounts of vhydrogen chloride.v Thus while the atomic ratio of chlorine to aluminum in fresh complex prepared with comercial alumay be introduced into the reactor through line 20. The, preferred hydrogen chloride recovery system. however, is that illustrated inthe drawv ing wherein the withdrawn complex is stripped minum chloride. may be of the order of about 2.72 the atomic ratio of chlorine to aluminum in complex withdrawn from the reactor after it has been on stream may be of the order -of 3.36. I have found that the additional hydrogen chloride which has obviously been taken up by the complex cannot be recovered therefrom in any appreciable amounts by any scrubbing or countercurrent contacting ywith liquid incoming charging stock but that it can be recovered al- '.wlll result in a completely vaporized stripping .2'0 4medium. No. pumps or compressors are required most quantitatively by stripping withdrawn comq plex with charging stock or product vapors 'at a temperature within the approximate rangev of 200 to 400 F. preferably about 300 to 400 F., e. g. about 350 F. More specifically I have found that by thus contacting withdrawn complex with an amount of charging stock or product vapors amounting to less than 10% of the total charge or product We may reduce the atomic ratio of chlorine to aluminum in the complex from 3.36 to about 2.7, i. e. I may reduce the hydrogen chloride content lto that present in the Ialuminum chloride used to make the complex. Since the operation of spent catalyst stripping is intermittent, the actual requirement is approximately one gallon of charging stock (or product) per daily barrel of reactor charge. The recovery of hydrogen chloride amounts to approximately .7 mol of hydrogen chloride per mol of aluminum chloride which is '5| to l0 times the recovery which could be eiected by scrubbing the complexy with f liquid charging stock. I offer no explanation for throughout a considerable range depending -on temperature, time of stripping, etc. When stripping during ones hour shift per day at about 350 F. I may vemploy about 1 to 10% by volume of the totalcharge or product stream, about2% vusually being suiicient but about 8% or about 130 to 140 barrels per day being employed in the specific example herein described. Where a suilcient amount of vapors are employed the' stripping may be leiected at temperatures as low as 100 F. but the viscosity of the complex usu-- ally makes such-low temperature stripping undesirable. The stripping may be eiected countercurrentlyand continuously, in which case the by a portion of the product vapors leaving the top of the product stripper reboiler.

Complex withdrawn from storage ltank 3| through line 4l and pump 42 or withdrawn di- .rectly from the reactor through lines 31 or 38 may be passed through lines 39 and 15 to complex stripper 16. This stripper may be a small cylindrical vessel about 2feet in diameter by about 10 feet in height for the specific example shown and may be provided with a. corrosion-resistant lining as in the case of the reactor.

base of complex stripper 16 through line 11 and reducing valve 80. This reduction in pressure in either rline 15 or line 11. The vapors which are introduced through line 11 and pass upwardly through complex stripper 16 leave the top of stripper 16 through line 18 and are conveyed thereby to line 46 for combination with the eluent product stream after thisstream has passed y through pressure reducing valve 45 and before` it enters after cooler 41. The stripping in stripper this case the stripping time should be within the l approximate range of 1 to 8 hours at a temperature in the general vicinity of 300 to 400 F.

The stripped complex withdrawn through line 19 is liquid at stripping temperature but becomes highly viscous and stii after cooling to room temperature, it can probably not be pumped at temperatures below about 150 F. Such spent complex may be hydrolyzed or otherwise treated or disposed of in anyiknown manner, but the substantial freedom from hydrogen chloride greatly simplies and facilitates such'disposal.

As a specific example of my system for pentane isomerization, the catalyst may be prepared in storage tank 3l and introduced by pump 42 into reactor 2| to a level of about 20 or 25 feet. About 1725 barrels per day of pentane charging stock which is substantially free from olens and which v within the approximate range of .100 to 250 F amount of vapors rquiredmay be very small,

. materially below 1% of stock charged or product produced. If the stripping with charging stock vaporsis at suiliciently high pressure these vapors together with recovered hydrogen chloride based on charging stock and,

contains less than 10%, preferably less than 5% -oi hexanes and heavier hydrocarbons is pumped by pump I4y through preheater I9 to reactor 2l along with about 9 barrels per day of benzene from source I1. Generally speaking, the amount of benzene may range from about .1 to 2% by volume based on charging stock. v Make-up aluminum chloride is introduced at the rate of about 1200 pounds per stream day.

'I'he reactor may be operated at temperatures or more but it is preferably operated at about to 200 F. under a'pressure of the order of 200 to 500 pounds per square inch, for example Vabout 30() pounds perI square inch. The space velocity may 'bewithin the approximate range of .4 to 4 volumes of charging stock per volume of catalyst complex in the reactor per hour. Hydrogen chloride introduced through line 24A may,

amount to about 1 to 20% or more of the weight forexample', may

be about 5 to 10%. Without the use of my com plex stripper 16 or equivalent means for recover-l A small amount 'of the material from line 65 is introduced in the .stream day of aluminum chloride.

ing hydrogen chloride, the make-up hydrogen 'chloride requirements amounted to about 360 pounds per day. By virtue of my invention this requirement is reduced to about 100 pounds per While my invention has been described in connection with specific processes and speciiic catalysts it should be understood that the invention is applicable to any process wherein a spent active Imetal halide complexassociated with substantial amounts of hydrogen halide must be withdrawn from a conversion system. Even in lsystems where aluminum chloride is supported on solid carriers there is usually a certainamount of hydrogen chloride-rich complex produced and hydrogen chloride may be recovered from such complex and returned to the system in the manner hereinabove described. Other modications and applications of the invention and alternative operating conditions .will be apparent to those skilled in the art from the above description.

operates at a top temperature in this case of about 130 F., a bottom temperature of about f 340 F., and a pressure of about 335 pounds lper square inch. The stripped product is then cooled and caustic washed and about 1740 barrels per day are withdrawn through line 14 for fractionation, storage cr blending.

I Heat is supplied-at the base of the stripper by reboiler 64 and the vapors which leave the top of the reboiler through` 'line 65 may be at a temperature of about 350 to 400 F. Hot vapors from this line are withdrawn in small amounts, e. g. about 130 to!y 140 barrels per day or less, regulated by flow controller B10 to the base of complex stripper 'lliv which contains excess catalyst withdrawn from the reactor or storage tank.

This excess catalyst results from the fresh additional complex in the reactor brought about by the addition of the approximatelZOO pounds per Since the pressures in reactor 2l and stripper 51 are both substantially in excess of the pressure in line 46, the stripping vapors from line 11 may be returned to the system without the necessity of pumps or compressors. As above stated, the stripping time may be of the order of l to 8 hours, preferably at least 4 hours, and the temperature should be of the order of 300 to 400 F. or in the general vicinity of 350` F. By this simple expedient enormous savings are eiected in hydrogen chloride requirements.

When my system is employed for butane isom- -erization the general iiow and'reaction conditions may be substantially lthe same as in theV 'IB will thus be less frequent in the case of butane than in the case of pentane because of the lesser amount of complex that must be disposed of. Here again, however, substantial savings may be effected in hydrogen chloride requirements.

My invention is also applicable to the recovery of hydrogen chloride from complex produced in the isomerization of light naphtha fractions, hex' anes, heptanes, etc., but in the case the conversion is usually at higher pressures and is eiected in the presence of added hydrogen. The charging stock or product vapors employed for stripping the withdrawn complex may be readily condensed l and pumped as a liquid into the high pressure reactor or into the eluent product stream after the pressure thereon has been reduced.

I claim: 1. In an aluminum chloride conversion process wherein a hydrocarbon is contacted with an alu- 'minum chloride catalyst in the presence of added hydrogen chloride to eiect conversion of said hydrocarbons in a contacting zone and-production of 'an aluminum chloride-hydrocarbon complex rich in hydrogenv chloride, the improved methodof operationwhich comprises withdrawing complex from said contacting zone and introducing it into a vcomplex stripping zone, withdrawing an eiliuent product stream from said contacting zone and introducing it into a product stripping zone, withdrawing hydrocarbons from the base of said product stripping zone, heating the withdrawn hydrocarbons to obtain at least partial vaporization thereof and returning the major portion of said heated hydrocarbons to the base of said product stripping zone, introducing a. small part of the heated hydrocarbons in vapor form at a low point in said complex stripping zone, stripping said complex with said vapors in said stripping zone and combining vapors from said complex stripping` zone with said eluent product stream.

2. 'I'he method of claim l which includes the step of maintaining the complex stripping zone at a lower pressure than the pressure maintained in the contacting zoneV and the product stripping zone respectively, decreasing the pressure of the eflluent product stream, combining vapors from said complex stripping zone with said etlluent product stream after the pressure on said product stream has been reduced andsubsequently pumping said product stream to said product stripping zone.

3. In apparatus for effecting hydrocarbon conversion a catalytic contacting'chamber, aproduct stripping tower, a complex stripping tower, means for passing a hydrocarbon charging stock and hydrogen chloride through said contacting chamber in contact with an aluminum chloride catalyst whereby an aluminum'chloride-hydrocarbon complex rich in hydrogen chloride is produced,

4means for introducing complex from said con.

said reboiler back to said product stripping tower,

means for introducing vapors from the top of said reboiler to the base of said complex stripping tower, means for withdrawing stripped complex from said product stripping tower and means for introducing vapors from said complex stripping tower to the efliuent product transfer means at a point subsequent to said pressure reducing Valve. n

4. In a process wherein an aluminum chloridevhydrocarbon complex rich in hydrogen chloride is produced in a conversion zone along with a hydrocarbon product'containing dissolved hydrogen chloride, the method of recovering hydrogen clrloride from said complex which comprises introducing said product into a stripping zone, reboiling product liquid at the base of said stripping zone, withdrawing complex from said conversion zone to a complex stripping zone and stripping said complex in said last-named zone with vapors from the reboiling/step. K

5. A pentane isomerization process which comprises passing a pentane charging stock along with a substantial amount of addedhydrogen chloride upwardly through a column of aluminum chloride-hydrocarbon complex catalyst having a heat of hydrolysis Within an approximate range of 300 to 400 calories per gram ofcomplex while maintaining said column at a temperature within the approximate range of 100 to 250 F. and under a pressure within the range of 100 to 500 pounds per square inch at a space velocity within the approximate range of .4 to 4 volumes of charging stock per hour per volume of .complex in the conversion zone, eiecting said contacting in the presence of about .1 to 2% of added benzene, withdrawing a product stream from the upper part of said conversion zone, reducing the pressure on the withdrawn stream, cooling said stream, separating catalyst material from the cooled stream, then pumping'said stream through a product stripping zone ata pressure slightly higher than the pressure of said conversion zone, reboiling liquids in thebase of said stripping zone to supply heat to said zone for removing hydrogen chloride, returning removed hydrogen vchloride to said conversion' zone, withdrawing complex from said conversion zone to a complex stripping zone, introducing vapors from said reboiling step to a low point in said complex stripping zone and introducing vapors from the top of said complex stripping'zone into the, eiiiuent product stream after the pressure on said stream has been reduced and before'saidstreamv has been 4returned to the product stripping zone. 'I

6. In 'a hydrocarbon conversion process which results in the production of spent aluminum chloride catalyst material containing hydrogen chloride and a hydrocarbon product stream containing dissolved hydrogen chloride, the method of operation which comprises passing said product stream in liquid phase through a rst stripping zone, heating said stream. at the base of said first stripping zone to a temperature approximating the boiling point of hydrocarbons in said stream whereby hydrogen chloride is dispelled from said stream, introducing spent hydrogen chloridecontaining catalyst material into a second. stripping zone, maintaining the second stripping zone at a lower pressure than the first stripping zone, and passing hydrocarbon heated to approximately its boiling point from the base of the Afirst stripping zone to the base of the second stripping zone with sulcient pressure reduction to insure substantially complete vaporization thereof when said hydrocarbon enters the second stripping zone.

JOHN E. SWEARINGEN.

REFERENCES CITED The following references are of rcord in the iile of this patent: i

UNITED STATES PATENTS 

